- A+
所属分类：Web前端
ref
<div ref = {( box )=>{ this.box = box }}></div> console.log(this.box); // 获取dom 生命周期(针对于组件而言)
Mounting 挂载顺序
constructor(props)：初始化 state 和 props 数据componentWillMount()在组件即将被挂载到页面时执行(16.3已废弃)- 新增
static getDerivedStateFromProps(props, state) render()：渲染组件componentDidMount()：在组件被挂载到页面后执行，只在挂载时执行一次
Updation 更新顺序
static getDerivedStateFromProps(props, state)shouldComponentUpdate()：在组件被更新之前执行 (return true 更新 , return false 不更新)render()： 渲染页面static getSnapshotBeforeUpdate(prevProps, prevState)componentDidUpdate()：state或props更新后调用
Unmounting 卸载
componentWillUnmount()在组件即将被页面剔除时执行
注意
除了render函数，其他所有的生命周期函数都可以没有
CSSTransition 动画库
安装
yarn add react-transition-group
使用
js
import { CSSTransition } from 'react-transition-group'; class TodoList extends Component { constructor(props) { super(props); this.state = { show: true, }; } render() { return ( <div> <CSSTransition in={this.state.show} timeout={1000} appear={true} unmountOnExit classNames="mydemo"> <p>hello</p> </CSSTransition> <button onClick={this.toggle.bind(this)}>提交</button> </div> ); } toggle() { this.setState(() => ({ show: !this.state.show, })); } } css
.mydemo-enter, .mydemo-appear { opacity: 0; } .mydemo-enter-active, .mydemo-appear-active { opacity: 1; transition: opacity 1s ease-in; } .mydemo-enter-done { opacity: 1; } .mydemo-exit { opacity: 1; } .mydemo-exit-active { opacity: 0; transition: opacity 1s ease-in; } .mydemo-exit-done { opacity: 0; } Ant Design UI库
安装
yarn add antd
使用
import { Input, Button, List } from 'antd'; import 'antd/dist/antd.css'; <Input placeholder="Basic usage"/> <Button type="primary">提交</Button> Redux
Redux = Reducer + Flux
安装
yarn add redux
原则
- store是唯一的
- 只有store能改变自己的内容(store里的数据不是reducer更新的)
- reducer必须是纯函数
核心API
- createStore (创建store)
- store.dispatch(action); (派发action给store)
- store.getState(); (获取store中所有的数据)
- store.subscribe (监听store，store发生改变时，自动触发)
具体用法
store/list.js
import store from './store/index'; import { changeInputAction } from './store/actionCreator'; class List extends Component { constructor(props) { super(props); this.state = store.getState(); store.subscribe(this.storeChange.bind(this)); // store发生改变时，自动触发 } render() { return ( <div> <input value={this.state.value} onChange={this.change.bind(this)} /> </div> ); } storeChange() { this.setState(store.getState()); } change(e) { // const action = { // type: 'change_input', // value: e.target.value, // }; const action = changeInputAction(e.target.value); store.dispatch(action); } } export default NewTodoList; store/actionCreator.js
action的统一管理
export const changeInputAction = value => ({ type: 'change_input', value, }); store/index.js
import { createStore } from 'redux'; import reducer from './reducer'; const store = createStore(reducer, window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ && window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__()); export default store; store/reducer.js
const defaultState = { value: '' }; export default (state = defaultState, action) => { console.log(state, action); let newState = JSON.parse(JSON.stringify(state)); // 深拷贝,不能直接修改state里的数据 if (action.type === 'change_input') { newState.value = action.value; } return newState; }; Redux-thunk中间件
Redux-thunk可以使action可以返回函数，从而在store/actionCreator.js中可以进行异步请求(axios)
安装
npm install redux-thunk
或
yarn add redux-thunk
使用
store/index.js
import { createStore, applyMiddleware, compose } from 'redux'; import thunk from 'redux-thunk'; import reducer from './reducer'; // window.__REDUX_DEVTOOLS_EXTENSION__ 可使用Redux DevTools插件 const composeEnhancers = window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ ? window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__({}) : compose; // 使用Redux-thunk中间件 const enhancer = composeEnhancers(applyMiddleware(thunk)); // 创建store const store = createStore(reducer, enhancer); export default store; TodoList.js
import { Component, Fragment } from 'react'; import { List } from 'antd'; import store from './store/index'; import { getTodoList } from './store/actionCreator'; class TodoList extends Component { constructor(props) { super(props); this.state = store.getState(); // store.subscribe(this.storeChange.bind(this)); // store发生改变时，自动触发 } render() { <Fragment> <List bordered dataSource={this.state.list} renderItem={(item, index) => <List.Item> {item} </List.Item>} /> </Fragment> } componentDidMount() { // 使用redux-thunk后，action可以返回函数，用于进行异步请求(axios) const action = getTodoList(); store.dispatch(action); } } export default TodoList; store/actionCreator.js
import axios from 'axios'; export const initListAction = list => ({ type: 'init_list', list, }); // 使用redux-thunk后，action可以返回函数，用于进行异步请求(axios) export const getTodoList = () => { return dispatch => { let list = []; axios.get('https://www.fastmock.site/mock/0764b93cba70add273910b232c51aad8/development/api/getHotList').then(function (res) { if (res.data.data.length > 0) { for (const val of res.data.data) { list.push(val.name); } } const action = initListAction(list); dispatch(action); // 将action传给store }); }; }; store/reducer.js
const defaultState = { list: [] }; export default (state = defaultState, action) => { console.log(state, action); let newState = JSON.parse(JSON.stringify(state)); // 深拷贝,不能直接修改state里的数据 if (action.type === 'init_list') { newState.list = action.list; } return newState; }; Redux-saga中间件
安装
npm install redux-saga --save
或
yarn add redux-saga
使用
1. 创建、使用、运行Redux-saga中间件
src/store/index.js
import { createStore, applyMiddleware, compose } from 'redux'; import thunk from 'redux-thunk'; import createSagaMiddleware from 'redux-saga'; import reducer from './reducer'; import sagas from './sagas'; // 创建sagas.js // window.__REDUX_DEVTOOLS_EXTENSION__ 可使用Redux DevTools插件 const composeEnhancers = window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ ? window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__({}) : compose; // 创建Redux-saga中间件 const sagaMiddleware = createSagaMiddleware(); // 使用Redux-thunk中间件、Redux-saga中间件 const enhancer = composeEnhancers(applyMiddleware(thunk, sagaMiddleware)); // 创建store const store = createStore(reducer, enhancer); // 运行saga中间件 sagaMiddleware.run(sagas); export default store; 2. 创建sagas.js
src/store/sagas.js
import { put, takeEvery } from 'redux-saga/effects'; import axios from 'axios'; import { initListAction } from './actionCreator'; // generator 函数 function* mySaga() { // 接收 store.dispatch() 传过来的action // 接收到get_init_list的action后，会调用getInitList方法 // getInitList可以执行异步操作 yield takeEvery('get_init_list', getInitList); } function* getInitList() { let list = []; const res = yield axios.get('https://www.fastmock.site/mock/0764b93cba70add273910b232c51aad8/development/api/getHotList'); // 等待axios请求结束后，直接将结果赋值给res if (res.data.data.length > 0) { for (const val of res.data.data) { list.push(val.name); } } const action = initListAction(list); yield put(action); // 类似于store.dispatch(action); } export default mySaga; 3. action的统一管理
src/store/actionCreator.js
export const initListAction = list => ({ type: 'init_list', list, }); 4. Reducer
src/store/reducer.js
const defaultState = { list: [], }; export default (state = defaultState, action) => { let newState = JSON.parse(JSON.stringify(state)); // 深拷贝,不能直接修改state里的数据 if (action.type === 'init_list') { newState.list = action.list; } return newState; }; 5. List.js
import { Component, Fragment } from 'react'; // 占位符 import store from './store/index'; import { List } from 'antd'; import 'antd/dist/antd.css'; class NewTodoList extends Component { constructor(props) { super(props); this.state = store.getState(); store.subscribe(this.storeChange.bind(this)); // store发生改变时，自动触发 } render() { return ( <Fragment> <List bordered dataSource={this.state.list} renderItem={(item, index) => <List.Item> {item} </List.Item>} /> </Fragment> ); } componentDidMount() { const action = { type: 'get_init_list', }; store.dispatch(action); // action不仅会被reducer接收，还会被redux-saga接收 } storeChange() { this.setState(store.getState()); } } export default NewTodoList; React-redux 第三方模块
安装
npm install react-redux --save
或
yarn add react-redux
使用
Provider组件
provider包裹在根组件外层，使所有的子组件都可以拿到state
- Provider连接了store
- Provider内部的所有组件都可以使用store
src/index.js
import React from 'react'; import ReactDOM from 'react-dom'; import { Provider } from 'react-redux'; import './index.css'; import store from './store'; import App from './App'; import reportWebVitals from './reportWebVitals'; ReactDOM.render( <Provider store={store}> <App /> </Provider>, document.getElementById('root') ); reportWebVitals(); connect连接store
- mapStateToProps: 把state数据映射到props中,这样在jsx中就可以用this.props.value来代替this.state.value获取值
- mapDispatchToProps: 把store.disptch()挂载到props上,这样在jsx中就可以用this.props.changeInput来代替store.disptch()改变store里的数据
src/List.js
import { Component, Fragment } from 'react'; import { connect } from 'react-redux'; class List extends Component { render() { return ( <Fragment> <div> <label htmlFor="input">输入内容</label> <input id="input" type="text" value={this.props.value} onChange={this.props.changeInput} /> </div> </Fragment> ); } } // 把state数据映射到props中 // 这样在jsx中就可以用this.props.value来代替this.state.value获取值 const mapStateToProps = state => { return { value: state.value, }; }; // 把store.disptch()挂载到props上 // 这样在jsx中就可以用this.props.changeInput来代替store.disptch()改变store里的数据 const mapDispatchToProps = disptch => { return { changeInput(e){ const action = { type: 'change_input', value: e.target.value, }; disptch(action); } }; }; export default connect(mapStateToProps, mapDispatchToProps)(List); // List连接store Reducer
src/store/reducer.js
const defaultState = { value: '' }; export default (state = defaultState, action) => { let newState = JSON.parse(JSON.stringify(state)); // 深拷贝,不能直接修改state里的数据 if (action.type === 'change_input') { newState.value = action.value; } return newState; }; 
